| 摘要 |
Nineteen strains of Lactobacillus, 2 strains of Lactococcus, 1 strain of Pediococcus, 4 strains of Propionibacterium and 23 strains of Bifidobacterium were screened for their ability to produce conjugated linoleic acid (CLA) from linoleic acid. Of these, 7 strains of Bifidobacterium, as well as 2 strains of Propionibacterium produced the cis-9, trans-11 CLA isomer from linoleic acid. In contrast, strains of Lactobacillus, Lactococcus and Pediococcus lacked the ability to synthesise CLA. CLA (cis-9, trans-11 isomer) production by the genus Bifidobacterium was shown to exhibit considerable interspecies variation, with B. breve and B. dentium being the most efficient producers among the strains tested, yielding up to 65 % conversion of linoleic acid to CLA at linoleic acid concentrations of 0.2-1.0 mg/ml in MRS medium. The growth of B. breve strains was inhibited by increasing concentrations of linoleic acid. Viability of B. breve 2257 was unaffected in the presence of up to 0.5 mg/ml linoleic acid for 48 h but was dramatically reduced to 1.5% survival at 1 mg/ml linoleic acid. However, viability of the B. breve strains NCFB2258, NCTC 11815, NCIMB 8815 and NCIMB 8807 was reduced to < 60 % at linoleic acid concentrations of 0.2 mg/ml. These data suggest that certain strains of bifidobacteria may have applications to elevate CLA content of food products and CLA status in humans. |
